Despite intensive efforts to increase participation in cancer clinical trials, fewer than two percent of US adults are enrolled in clinical trials. Over 4% of National Cancer Institute-sponsored cooperative group trials fail to complete accrual. Clinical trial eligibility criteria present one of the most significant barriers to study accrual and one ofthe few accrual factors directly controlled by investigators and sponsors. Over time, these criteria have become more numerous and restrictive. Across cancer types, a history of prior cancer is a widespread exclusion criterion in clinical trials. This common practice reflects concerns that a prior cancer diagnosis could interfere with study conduct or outcomes, but there are no data clearly supporting these assumptions. Because this practice hinders accrual, limits generalizability of findings, and discriminates against cancer survivors, we need to understand its basis and implications. In a preliminary analysis, we found that approximately 80% of industry- and government-sponsored lung cancer trials exclude patients with prior cancer. For some trials, we projected that over 18% of lung cancer patients would be excluded for this reason alone, corresponding to more than 200 excluded patients for some large phase 3 trials. The goal of the proposed study is to determine the prevalence and impact of prior cancer among older patients with lung cancer using a large, representative, population-based US dataset. Given the large and growing number of cancer survivors, this research will have important and immediate impact on lung cancer clinical trial design and conduct. For example, if we document equivalent or better survival for those with prior cancer, investigators and sponsors could change or modify this exclusion criterion. In turn, this will increase study accrual and completion rates, resulting in getting better treatments to more patients sooner.